In recent years, mobile communication services have expanded and increased in popularity, around the world. Mobile stations and networks were originally developed and deployed for voice telephone type communications and then for communication of relatively short text messages. However, as broadband multimedia services have evolved and expanded, the demand for such services has included an ever-increasing demand for broadband communications in the mobile environment. To meet evolving demands, the service providers and their equipment vendors have developed and deployed a series of ever more sophisticated mobile networks and mobile stations. Many geographic areas are now served by network technologies considered as third generation (3G) or even fourth generation (4G) in terms of the wireless technology. In that regard, some of the more advanced carriers are now in early stages of deploying elements of a Long-Term Evolution (LTE) type mobile communication network.
In wireless cellular communication systems, such as Code Division Multiple Access (CDMA), Evolution-Data Optimized (EVDO) and other systems, each cell broadcasts information about its geographically adjacent cells or neighbor cells. Information about neighbor cells is used by user equipment (UE) and/or a network for UE handoff between cells or cell selection by or for a UE. In some wireless cellular communication systems (e.g., 3G and EVDO), the neighbor cell information is typically broadcast as a neighbor cell list to UEs for performing handoff operations. In such cases, the UEs typically maintain local copies of the latest received neighbor cells list, and make and report received signal strength measurements on the cells identified in the list of neighbor cells.
However, in the LTE type mobile communication network, a serving cell (or base station) does not provide the UE with the list of neighbor cells. Instead, the UE scans all possible neighbor cells having cell identifier information (e.g., Physical Cell Identity (PCI), Pseudo Noise (PN) code, or frequency value) and makes handoff analysis and requests on those detected. After measuring the received signal strength on the candidate neighbor cells, the UE reports the measurement results to the network for a potential handoff when the signal strength of the serving cell reaches a certain threshold value during a call connection to the network.
As mentioned earlier, the UE scans all possible cells with PCI. The scanning operation by the UE is not limited by its processing power. If the UE sees a cell with a particular PCI that the UE wants to handoff off a call session to, the UE asks the network to do so. In this case, if the network does not know about the cell with the PCI that the UE is requesting for handoff operation, because the cell is not a neighbor cell in the list of neighbor cells, then the UE will not be allowed to make the handoff and the call session will drop as a result. In addition, if the UE is not allowed to make the handoff because the network does not have resources to set up and the base station does not know about, the network just ignores the reported PCI measurements by the UE. In the case, where the UE detects received signals to compile a neighbor list (or a list of neighbor cells), the list of neighbor cells is often limited by the UE's processing capability and/or memory capacity of the equipment. Hence, in the existing LTE technique, making the neighbor list accurate and as short as possible is of primary importance. As a result, the existing technique sometimes leads to missing neighbor cells and thus leads to failed or degraded mobility, because occasionally neighbor cells that are not likely to be inserted into the list of neighbor cells will be needed for handoff operation by the UE.
In another approach in the existing wireless cellular communication systems, the list of neighbor cells is established by a network using a self-optimization technique which utilizes long term statistics of traffic data collected in the network under normal operation. Thus, the self-optimization technique requires a live network and a considerable amount of historical traffic data for performing statistical analysis and building a list of neighbor cells. That is, based on the statistical analysis of traffic data and handoff data in a “mature” network, the list of neighbor cells for a cell site is established by adding or removing candidate cells for the neighbor list. As a result, during an initial deployment stage of a wireless cellular communication network, such as a LTE type communication network, where a collection of historical traffic data is not often available in the beginning for statistical analysis, the existing techniques (e.g., self-optimization based or statistical analysis based techniques) for establishing a list of neighbor cells have become ineffective and often miss neighbor cells, thereby causing performance issues (e.g., failed or degraded mobility). Also, the list of neighbor cells can be established manually by operators based on Radio Frequency (RF) measurements, test driving and simulations, but this requires a considerable amount of time and operator efforts and can also lead to a missing neighbor cell issue.
Hence, a need exists for automatically establishing an accurate list of neighbor cells for a cell site in an early deployment stage of a LTE type mobile communication network, where a historical collection of traffic data is not available yet for statistical analysis and self-optimization based techniques.